Regeneration of ionic liquid catalyst using a metal in the absence of added hydrogen

ABSTRACT

A process for regenerating a used acidic ionic liquid catalyst comprising contacting the used ionic liquid catalyst with at least one metal in a regeneration zone in the absence of added hydrogen under regeneration conditions for a time sufficient to increase the activity of the ionic liquid catalyst is described. In one embodiment, regeneration is conducted in the presence of a hydrocarbon solvent.

FIELD OF THE INVENTION

The present invention relates to methods for the regeneration ofcatalysts and more specifically to the regeneration of ionic liquidcatalysts.

BACKGROUND OF THE INVENTION

Ionic liquids are liquids that are composed entirely of ions. Theso-called “low temperature” Ionic liquids are generally organic saltswith melting points under 100 degrees C., often even lower than roomtemperature. Ionic liquids may be suitable for example for use as acatalyst and as a solvent in alkylation and polymerization reactions aswell as in dimerization, oligomerization acetylation, metatheses, andcopolymerization reactions.

One class of ionic liquids is fused salt compositions, which are moltenat low temperature and are useful as catalysts, solvents andelectrolytes. Such compositions are mixtures of components which areliquid at temperatures below the individual melting points of thecomponents.

Ionic liquids can be defined as liquids whose make-up is entirelycomprised of ions as a combination of cations and anions. The mostcommon ionic liquids are those prepared from organic-based cations andinorganic or organic anions. The most common organic cations areammonium cations, but phosphonium and sulphonium cations are alsofrequently used. Ionic liquids of pyridinium and imidazolium are perhapsthe most commonly used cations. Anions include, but not limited to,BF₄—, PF₆—, haloaluminates such as Al₂Cl₇ ⁻ and Al₂Br₇ ⁻,[(CF₃SO₂)₂N)]⁻, alkyl sulphates (RSO₃—), carboxylates (RCO₂—) and manyother. The most catalytically interesting ionic liquids are thosederived from ammonium halides and Lewis acids (such as AlCl₃, TiCl₄,SnCl₄, FeCl₃ . . . etc). Chloroaluminate ionic liquids are perhaps themost commonly used ionic liquid catalyst systems.

Examples of such low temperature ionic liquids or molten fused salts arethe chloroaluminate salts. Alkyl imidazolium or pyridinium salts, forexample, can be mixed with aluminum trichloride (AlCl₃) to form thefused chloroaluminate salts. The use of the fused salts of1-alkylpyridinium chloride and aluminum trichloride as electrolytes isdiscussed in U.S. Pat. No. 4,122,245. Other patents which discuss theuse of fused salts from aluminum trichloride and alkylimidazoliumhalides as electrolytes are U.S. Pat. Nos. 4,463,071 and 4,463,072.

U.S. Pat. No. 5,104,840 to describes ionic liquids which comprise atleast one alkylaluminum dihalide and at least one quaternary ammoniumhalide and/or at least one quaternary ammonium phosphonium halide andtheir uses as solvents in catalytic reactions.

U.S. Pat. No. 6,096,680 describes liquid clathrate compositions usefulas reusable aluminum catalysts in Friedel-Crafts reactions. In oneembodiment, the liquid clathrate composition is formed from constituentscomprising (i) at least one aluminum trihalide, (ii) at least one saltselected from alkali metal halide, alkaline earth metal halide, alkalimetal pseudohalide, quaternary ammonium salt, quaternary phosphoniumsalt, or ternary sulfonium salt, or a mixture of any two or more of theforegoing, and (iii) at least one aromatic hydrocarbon compound.

Aluminum-containing catalysts are among the most common Lewis acidcatalysts employed in Friedel-Craft reactions. Friedel-Craft reactionsare reactions which fall within the broader category of electrophylicsubstitution reactions including alkylations.

Other examples of ionic liquids and their methods of preparation mayalso be found in U.S. Pat. Nos. 5,731,101; 6,797,853 and in U.S. PatentApplication Publications 2004/0077914 and 2004/0133056.

As a result of use, ionic liquid catalysts become deactivated, i.e. loseactivity, and may eventually need to be replaced. However, ionic liquidcatalysts are expensive and replacement adds significantly to operatingexpenses by in some cases requiring shut down of an industrial process.One of the heretofore unsolved problems impeding the commercial use ofchloroaluminate ionic liquid catalysts has been the inability toregenerate and recycle them. The present invention provides methods toregenerate acidic chloroaluminate ionic liquid catalysts overcoming thisobstacle and paving the way for the practical, commercial use of theseenvironmentally friendly catalysts.

SUMMARY OF THE INVENTION

The present invention, among other things, provides a process forregenerating a used acidic ionic liquid catalyst comprising contactingthe used ionic liquid catalyst with at least one metal in a regenerationzone in the absence of added hydrogen under regeneration conditions fora time sufficient to increase the activity of the ionic liquid catalyst.In one embodiment, regeneration is conducted in the presence of ahydrocarbon solvent.

DETAILED DESCRIPTION

The present invention relates to a process for the regeneration of spentor deactivated acidic ionic liquid-based catalysts i.e. those catalystswhich have lost all or some of their catalytic activity. The presentprocess is being described and exemplified with reference certainspecific ionic liquid catalysts and processes catalyzed thereby, butsuch description is not intended to limit the scope of the invention.The methods described may be applied to other catalysts and processes bythose persons having ordinary skill based on the teachings, descriptionsand examples included herein.

The specific examples used herein refer to alkylation processes usingionic liquid systems, which are amine-based cationic species mixed withaluminum chloride. In such systems, to obtain the appropriate aciditysuitable for the alkylation chemistry, the ionic liquid catalyst isgenerally prepared to full acidity strength by mixing one molar part ofthe appropriate ammonium chloride with two molar parts of aluminumchloride. The catalyst exemplified for the alkylation process isa1-alkyl-pyridinium chloroaluminate, such as 1-butyl-pyridiniumheptachloroaluminate.

In general, a strongly acidic ionic liquid is necessary for isoparaffinalkylation, e.g. isoparaffin alkylation. In that case, aluminumchloride, which is a strong Lewis acid in a combination with a smallconcentration of a Broensted acid, is a preferred catalyst component inthe ionic liquid catalyst scheme.

While not being bound to this or any other theory of operation, thepresent invention is based in part on our discovery that one of themajor catalyst deactivation mechanisms is the formation of by-productsknown as conjunct polymers. The term conjunct polymer was first used byPines and Ipatieff to distinguish these polymeric molecules from theusual polymers. Unlike typical polymers, conjunct polymers arepolyunsaturated cyclic, polycyclic and acyclic molecules formed byconcurrent acid-catalyzed reactions including, among others,polymerization, alkylation, cyclization, and hydride transfer reactions.Conjunct polymers consist of unsaturated intricate network of moleculesthat may include one or a combination of 4-, 5-, 6- and 7-membered ringsin their skeletons. Some examples of the likely polymeric species werereported by Miron et al. (Journal of chemical and Engineering Data,1963) and Pines (Chem. Tech, 1982). These molecules contain double andconjugated double bonds in intricate structures containing a combinationof cyclic and acyclic skeletons.

The conjunct polymers deactivate the chloroaluminate ionic liquidcatalysts by weakening the acid strength of the catalyst through theformation of complexes of conjunct polymers and AlCl₃ possibly by meansof electron-donor/electron-acceptor interactions. The conjunct polymerswith their double bonds are the donors and the Lewis acid (AlCl₃) is theacceptor. Using their double bonds, the conjunct polymers coordinate tothe Lewis acid (AlCl₃) in the ionic liquid and rendering thebutylpyridinium chloroaluminate catalyst less active. Conjunct polymersproduced by the HCl-promoted chloroaluminate ionic liquid-catalyzedalkylations are chlorinated molecules. Therefore, in addition toacid-base complexation described earlier, aluminum chloride may reactwith the chlorinated molecules to make R⁺AlCl₄ ⁻ intermediates. Thesecomplexation pathways and perhaps other complexing mechanisms depletethe concentration of the Lewis acid in the ionic liquid and thus, theacidity of the catalyst becomes weaker and the overall catalyticactivity becomes compromised and no longer effective for the intendedpurpose. Thus, the catalyst performance will become a function of theconcentration of conjunct polymers in the ionic liquid phase. As moreconjunct polymers accumulate in the ionic liquid phase the catalystbecomes less active. So, removal of all or a suitable portion of theconjunct polymers from the ionic liquid phase is a significant aspect ofthe present process for ionic liquids catalyst regeneration.

The term “conjunct polymer” as used herein also includes any otherspecies which might complex to AlCl₃ by pi bonding or sigma bonding orother means, which results in those species binding to the ionic liquid,so they are not removable by simple hydrocarbon extraction.

It is believed that deactivation of the catalyst by the presence ofconjunct polymers is, in part at least, caused by coordination andcomplex formation between the Lewis acid AlCl₃ (electron pair acceptor)and the conjunct polymers (electron donors). In such complexes, theAlCl₃ is no longer available for catalysis since it is tied-up in theAlCl₃-conjunct polymers complexes. It also appears that the presence (oraccumulation) of conjunct polymer molecules in the catalyst phase is notby virtue of being miscible in the ionic liquid phase. While conjunctpolymers may be somewhat miscible in the ionic liquids, theiraccumulation in the catalyst phase is more likely to being bound bystrong acid-base interactions (complexation) rather than being solublein the ionic liquid phase.

Conjunct polymers isolated from the catalyst phase by means ofhydrolysis are highly soluble in hydrocarbons. However, attempts toremove them from the catalyst phase prior to hydrolysis by simpleextraction methods with hydrocarbon solvents such as hexane, decane andtoluene were unsuccessful. Other more polar solvents such as CH₂Cl₂ maydissolve a chloroaluminate ionic liquid and therefore are not selectivesolvents for dissolving and removing conjunct polymers. Conjunctpolymers may be isolated by hydrolysis. However, these methods ofisolating the conjunct polymers are destructive, and result in an actualloss of a catalytic component (AlCl₃). The hydrolysis methods hydrolyzethe catalytic component (AlCl₃) and transform it into inactive aluminumhydroxide and aluminum oxide. This indicates that the conjunct polymersare tightly held in the ionic liquid phase by fairly strong type ofbonding system. Therefore, any successful attempt to reactivate andregenerate the catalyst must involve the removal of conjunct polymers torelease aluminum trichloride from the AlCl₃-conjunct polymer complexeswithout destroying, consuming, or irreversibly tying up the AlCl₃. Inother words, one objective is to free the catalyst by replacing theconjunct polymers with other basic species that simply displace thepolymer without destroying the catalyst or by suppressing the ability ofconjunct polymers to form complexes with Lewis acids (aluminumchloride).

The deactivated catalyst can be revived in a nondestructive manner byfreeing up the AlCl₃ from conjunct polymer—AlCl₃ complex. AlCl₃ nolonger bound by conjunct polymers is then released to take part incatalytic reactions.

Among other things, the present invention provides a process for theregeneration of used acidic ionic liquid catalysts in a nondestructivemanner by contacting a used ionic liquid catalyst with at least onemetal under regeneration conditions in the absence of added hydrogen soas to increase the activity of the used ionic liquid catalyst.

The metal used in this invention may be any one or more of a broad rangeof metals. Such metals may be selected from Groups VI-B, VIII, II-A andII-B. Specific examples of the metallic catalysts are Fe, Co, Ni, Ru,Rh, Pd, Ir, Os, Pt, Cr, Mn, Ti, V, Zr, Mo, W, B, Al, Ga, In, Tl, Zn, Cd,Cu, Ag and Au. These metals may be used singly, in combination or asalloys. Metals such as Raney nickel and alloys such as Ni/Al alloy mayalso be suitably employed. The metal may also be used alone or withother substances such as an inorganic oxide catalyst supports.

The metals may be in the form of fine particles, granules, sponges,gauzes, etc. Each metal may be used in any number of forms: (1)macroscopic, which includes wires, foils, fine particles, sponges,gauzes, granules, etc.; and (2) microscopic, which includes powders,smokes, colloidal suspensions, and condensed metal films.

An effective amount of metal is employed in the practice of the presentinvention. The amount of metal, say aluminum, added in the regenerationscheme is determined by the amount (concentration) of the conjunctpolymers in the spent ionic liquid catalyst. For example, the amount ofthe metal used for the regeneration of a given spent catalyst is usuallyadded in excess to the concentration of conjunct polymers present in thespent catalyst.

The metal selection for the regeneration is usually based on thecomposition of the ionic liquid catalyst. The metal should be selectedcarefully to prevent the contamination of the catalyst with unwantedmetal complexes or intermediates that may form and remain in thecatalyst phase. For example, aluminum metal will be the metal of choicefor the regeneration when the catalyst system is chloroaluminate ionicliquid-based catalyst. The use of any other metal may change the overallcomposition of the catalyst.

As noted previously, ionic liquid catalysts may become deactivatedduring use. For example, in an alkylate production unit, light (C₂-C₅)olefins and isoparaffin feeds are contacted in the presence of acatalyst that promotes the alkylation reaction. In one embodiment of aprocess in accordance with the present invention, this catalyst is achloroaluminate ionic liquid. The reactor, which may be a stirred tankor other type of contactor (e.g., riser reactor), produces a biphasicmixture of alkylate hydrocarbons, unreacted isoparaffins, and ionicliquid catalyst containing some conjunct polymers. The densecatalyst/conjunct polymer phase may be separated from the hydrocarbonsby gravity settling in a decanter. This catalyst will be partiallydeactivated by the conjunct polymers binding to AlCl₃. The recoveredcatalyst can be reactivated in a regeneration process according to thecurrent invention. The products of this step will be reactivatedcatalyst and conjunct polymers among others as described herein. Thereactivated catalyst and the conjunct polymers can be separated, forexample, by solvent extraction, decantation, and filtration.

In one embodiment of the present invention, a used ionic liquidcatalyst/conjunct polymer mixture is introduced continuously into aregeneration reactor, which contains a metal. Inert hydrocarbons inwhich conjunct polymers are soluble are fed into the reactor at thedesired rate. The inert hydrocarbons may be a normal hydrocarbonsranging from C₅-C₁₅ and their mixtures, preferably C₅-C₈ although otherhydrocarbons may be employed. The residence time, temperature andpressure of the reactor will be selected to allow the desiredreactivation of the ionic liquid catalyst. The reaction product iswithdrawn and sent to a separator. This mixture is then separated intothree streams, one comprising light hydrocarbons, a second comprisinginert hydrocarbons and conjunct polymers and a third comprisingregenerated ionic liquid catalyst. A gravity decanter is used toseparate the mixture, from which the ionic liquid phase, which is denserthan other components, is withdrawn. The reactivated ionic liquidcatalyst is returned to the alkylation reactor. The solvent/conjunctpolymer mix is separated by distillation to recover the solvent.

It is not necessary to regenerate the entire charge of catalyst. In someinstances only a portion or slipstream of the catalyst charge isregenerated. In those instances only as much ionic liquid catalyst isregenerated as is necessary to maintain a desired level of catalystactivity in the process in which the ionic liquid is used as thecatalyst.

Regeneration conditions will generally include temperatures of −20°C.-200° C., preferably 50°-100° C. pressures of atmospheric-5000 psig,preferably atmospheric-500 psig, and a contact time of 0.1 minute-24hours, and preferably from ¼-2 hours in a normal hydrocarbon as asolvent.

The following Examples are illustrative of the present invention, butare not intended to limit the invention in any way beyond what iscontained in the claims which follow.

EXAMPLES Example 1 Preparation of Fresh 1-ButylpyridiniumChloroaluminate Ionic Liquid Catalyst A (Fresh IL A)

1-butyl-pyridinium chloroaluminate is a room temperature ionic liquidprepared by mixing neat 1-butyl-pyridinium chloride (a solid) with neatsolid aluminum trichloride in an inert atmosphere. The syntheses ofbutylpyridinium chloride and the corresponding 1-butyl-pyridiniumchloroaluminate are described below. In a 2-L Teflon-lined autoclave,400 gm (5.05 mol.) anhydrous pyridine (99.9% pure purchased fromAldrich) were mixed with 650 gm (7 mol.) 1-chlorobutane (99.5% purepurchased from Aldrich). The neat mixture was sealed and let to stir at125° C. under autogenic pressure over night. After cooling off theautoclave and venting it, the reaction mix was diluted and dissolved inchloroform and transferred to a three liter round bottom flask.Concentration of the reaction mixture at reduced pressure on a rotaryevaporator (in a hot water bath) to remove excess chloride, un-reactedpyridine and the chloroform solvent gave a tan solid product.Purification of the product was done by dissolving the obtained solidsin hot acetone and precipitating the pure product through cooling andaddition of diethyl ether. Filtering and drying under vacuum and heat ona rotary evaporator gave 750 gm (88% yields) of the desired product asan off-white shiny solid. ¹H-NMR and ¹³C-NMR were consistent with thedesired 1-butyl-pyridinium chloride and no impurities were observed.

1-butylpyridinium chloroaluminate was prepared by slowly mixing dried1-butylpyridinium chloride and anhydrous aluminum chloride (AlCl₃)according to the following procedure. The 1-butylpyridinium chloride(prepared as described above) was dried under vacuum at 80° C. for 48hours to get rid of residual water (1-butylpyridinium chloride ishydroscopic and readily absorbs water from exposure to air). Fivehundred grams (2.91 mol.) of the dried 1-butylpyridinium chloride weretransferred to a 2-Liter beaker in a nitrogen atmosphere in a glove box.Then, 777.4 gm (5.83 mol.) of anhydrous powdered AlCl₃ (99.99% fromAldrich) were added in small portions (while stirring) to control thetemperature of the highly exothermic reaction. Once all the AlCl₃ wasadded, the resulting amber-looking liquid was left to gently stir for anadditional 1/2-1 hour. The liquid was then filtered to remove anyun-dissolved AlCl₃. The resulting acidic 1-butyl-pyridiniumchloroaluminate was used as the catalyst for the alkylation ofisoparaffins with olefins.

Example 2 Preparation of “Deactivated” 1-Butylpyridinium ChloroaluminateIonic Liquid Catalyst (Deactivated Catalyst A)

“Deactivated” or “used” 1-butylpyridinium chloroaluminate ionic liquidcatalyst was prepared from “fresh” 1-butylpyridinium chloroaluminateionic liquid catalyst by carrying out the isobutane alkylation reactionin a continuous flow microunit under catalyst recycle with acceleratedfouling conditions.

The microunit consists of feed pumps for isobutane and butenes, astirred autoclave reactor, a back pressure regulator, a three phaseseparator, and a third pump to recycle the separated ionic liquidcatalyst back to the reactor. The reactor was operated at 80 to 100 psigpressure and with cooling to maintain a reaction temperature of ˜10° C.To start the reaction, isobutane, butenes, and HCl were pumped into theautoclave at the desired molar ratio (isobutane/butenes >1.0), throughthe back pressure regulator, and into the three phase separator. At thesame time, fresh chloroaluminate ionic liquid catalyst was pumped intothe reactor at a rate pre-calculated to give the desired catalyst/feedratio on a volumetric basis. As the reaction proceeded, ionic liquidseparated from the reactor effluent and collected in the bottom of thethree phase separator. When a sufficient level of catalyst built up inthe bottom of the separator, the flow of fresh ionic liquid was stoppedand catalyst recycle from the bottom of the separator was started. Inthis way, the initial catalyst charge was continually used and recycledin the process.

The following process conditions were used to generate DeactivatedCatalyst A (1-butylpyridinium chloroaluminate ionic liquid catalyst)from Fresh

Catalyst A: Process Variable Isobutane pump rate 4.6 g/min Butene pumprate 2.2 g/min IL Catalyst pump rate 1.6 g/min HCl flow rate 3.0 SCCMpressure 100 psig temperature 10° C.

The reaction was continued for 72 hours when it was judged that thecatalyst had become sufficiently deactivated.

Example 3 Determination of the Amounts of Conjunct Polymer and OlefinOligomers in Deactivated IL A

The wt % of conjunct polymers in the spent (deactivated) ionic liquidwas determined by hydrolysis of known weights of the spent catalyst. Theexample below is a typical procedure for measuring conjunct polymers ina given spent catalyst. In a glove box, 15 gm of a spent ionic liquidcatalyst in a flask were rinsed first with 30-50 ml of anhydrous hexaneto remove (from the spent catalyst) any residual hydrocarbon or olefinicoligomers. The hexane rinse was concentrated under reduced pressure togive only 0.02 gm of yellow oil (0.13%). Then, 50 ml of anhydrous hexanewas added to the rinsed catalyst followed by slow addition of 15 ml ofwater, and the mixture was stirred at 0° C. for 15-20 minutes. Theresulting mixture was diluted with additional 30 ml hexanes and stirredwell for additional 5-10 minutes. The mixture was allowed to settle downto two layers solution and some solid residue. The organic layer wasrecovered by decanting. The aqueous layer was further washed withadditional 50 ml hexanes. The hexanes layers were combined and driedover anhydrous MgSO₄, filtered and concentrated to give 2.5 gm (16.7 wt% of the spent catalyst) of viscous dark orange-reddish oil. It wasdetermined therefore that this particular spent catalyst contains 0.13%oligomers and 16.7% conjunct polymers. The hydrolysis can also beaccomplished using acidic (aqueous HCl) or basic (aqueous NaOH)solutions.

Example 4 Characterization of Recovered Conjunct Polymer fromDeactivated IL A

The recovered conjunct polymers according to the procedure described inExample 3 were characterized by elemental analysis and by infrared, NMR,GC-Mass and UV and spectroscopy methods. The recovered conjunct polymershave hydrogen/carbon ratio of 1.76 and chlorine content of 0.8%. ¹H-NMRand ¹³C-NMR showed the presence of olefinic protons and olefiniccarbons. Infra Red indicated the presence of olefinic regions and thepresence of cyclic systems and substituted double bonds. GCMS showed theconjunct polymers to have molecular weights ranging from 150-mid 600s.The recovered conjunct polymers have boiling ranges of 350-1100° F. asindicated by high boiling simulated distillation analysis. UVspectroscopy showed a UV λ_(max) at 250 nm pointing highly conjugateddouble bonds systems.

Example 5 Regeneration of Chloroaluminate Ionic Liquid Catalysts byRemoval of Conjunct Polymers from the Spent Catalyst by using AluminumMetal in the Absence of Added Hydrogen

A 300 cc autoclave was charged with 51 gm of used (deactivated)butylpyridinium chloroaluminate ionic liquid containing 15.5 wt % (7.90gm) conjunct polymers, 65 ml hexane, and 8 gm aluminum powder. Theautoclave was heated to 100° C. while stirring with an overhead stirrerat 1200 rpm. The starting autogenic pressure of the reaction was 11 psiand rose to 62 psi once heating reached 100° C. and remained there forthe duration of the reaction. The reaction was allowed to run for 1.5hrs. The reaction was cooled down, and the reaction mixture wasseparated in the glove box where the organic layer was removed bydecantation. The ionic liquid-aluminum residue was rinsed with 2×50 mlanhydrous hexane. The hexane layers were all combined and dried overMgSO₄. Filtration and concentration of the dried hexane rinses gave 6.3gm 99.7% of the expected conjunct polymers as pale yellow oils. Theionic liquid catalyst was separated from aluminum by filtration.Hydrolysis of 10 gm portion of the filtered ionic liquid catalystfollowed by extraction with hexane showed no presence of conjunctpolymers in the treated spent ionic liquid. The reaction described abovewas repeated once more on the same spent catalyst and led to the removalof >98% of the conjunct polymers. The reaction was repeated on 52 gm ofspent butyl-pyridinium chloroaluminate catalysts containing 15.5 wt %(7.9 gm CPs) and led to removing 7.75 gm of the polymers (98.0%) fromthe spent catalyst. Hydrolysis of the regenerated ionic liquid catalystindicated the presence of <0.5% of conjunct polymers.

Example 6 Regeneration of Chloroaluminate Ionic Liquid Catalysts byRemoval of Conjunct Polymers from the Spent Catalyst by using Zinc Metalin the Absence of Added Hydrogen

The regeneration procedure of Example 5 above was repeated using excesszinc metal (8 grams zinc powder) instead of aluminum to regenerate 50.2gm of spent ionic liquid containing 24.3 wt % conjunct polymers (12.2gm). The reaction ran for 1.5 hours at 100° C. The autogenic pressurewas 13 psi at the start of reaction and 57 psi at the end. The use ofzinc resulted in the removal of 7.6 gm (62.3%) of the conjunct polymerspresent in the spent catalyst. The hydrolysis of the residual ionicliquid catalyst showed 2.6 gm of conjunct polymers remained in thecatalyst. The use of zinc led to a total removal of 10 gm (81%) of theconjunct polymers present in the spent catalyst.

Example 7 Regeneration of Chloroaluminate Ionic Liquid Catalysts byRemoval of Conjunct Polymers from the Spent Catalyst by using IndiumMetal in the Absence of Added Hydrogen

The regeneration procedure of Example 5 above was repeated but usingindium metal (8 grams) in place of aluminum for the regeneration of 50gm of spent catalysts containing 24.3 wt % conjunct polymers (12.15 gm).The reaction conditions were 100° C., 11/2 hours, and 13 psi (startingpressure)-57 psi (ending pressure). The use of indium resulted in theremoval of 10.8 gm (89%) of the conjunct polymers present in the spentcatalyst before regeneration.

Example 8 Regeneration of Chloroaluminate Ionic Liquid Catalysts byRemoval of Conjunct Polymers from the Spent Catalyst by using GalliumMetal in the Absence of Added Hydrogen

The regeneration procedure of Example 5 was repeated using gallium metal(8 gm) in place of aluminum metal to remove 24.3 wt % (12.15 gm)conjunct polymers from 50 gm spent butyl pyridinium chloroaluminatespent ionic liquid. The reaction stared at 14 psi pressure and ended at68 psi. Again, it ran for 11/2 hours at 100° C. The reaction resulted inthe removal of 45% (5.5 gm) of the conjunct polymers present in thespent catalyst before regeneration.

Based on the results discussed in the examples above, aluminum and othermetals appear to effectively remove conjunct polymers from the spentcatalyst without the need for added hydrogen. Without being bound to anytheory, it appears that the removal mechanism is probably driven by anoxidative-reductive reaction where the metals are oxidized and theconjunct polymers and their chlorinated analogues are reduced.

There are numerous variations on the present invention which arepossible in light of the teachings and supporting examples describedherein. It is therefore understood that within the scope of thefollowing claims, the invention may be practiced otherwise than asspecifically described or exemplified herein.

1. A process for regenerating a used acidic ionic liquid catalystcomprising contacting the used ionic liquid catalyst with at least onemetal in a regeneration zone in the absence of added hydrogen underregeneration conditions for a time sufficient to increase the activityof the ionic liquid catalyst.
 2. A process according to claim 1, whereinthe metal is selected from the group consisting of Groups VI-B, VIII,III-A and II-B elements and their mixtures.
 3. A process according toclaim 1, wherein the metal is selected from the group consisting ofaluminum, indium, gallium and zinc.
 4. A process according to claim 1,wherein the metal is in a microscopic form.
 5. A process according toclaim 1, wherein the metal is in a macroscopic form.
 6. A processaccording to claim 1, wherein the reaction zone contains an inerthydrocarbon in which conjunct polymers are soluble.
 7. A processaccording to claim 5, wherein the inert hydrocarbon is selected from thegroup consisting of normal hydrocarbons ranging from C₅-C₁₅ and theirmixtures.
 8. A process according to claim 1, wherein the ionic liquidcatalyst has been used to catalyze a Friedel-Craft reaction.
 9. Aprocess according to claim 8, wherein the Friedel-Craft reaction isalkylation.
 10. A process according to claim 1, wherein the ionic liquidcatalyst comprises an imidazolium, pyridinium, phosphonium ortetralkylammonium derivative or their mixtures.
 11. A process accordingto claim 1, wherein the ionic liquid catalyst is a chloroaluminate ionicliquid.
 12. A process according to claim 11, wherein the metal isaluminum.
 13. An ionic liquid catalyst, which has been regenerated inaccordance with the process of claim
 1. 14. A process for regenerating aused acidic ionic liquid catalyst which has been deactivated by conjunctpolymers comprising the steps of contacting the used ionic liquidcatalyst with at least one metal in a regeneration zone in the absenceof added hydrogen under regeneration conditions in the presence of aninert hydrocarbon in which conjunct polymers are soluble for a timesufficient to increase the activity of the ionic liquid catalyst.
 15. Aprocess according to claim 14, wherein the inert hydrocarbon is selectedfrom the group consisting of normal hydrocarbons ranging from C₅-C₁₅ andtheir mixtures.
 16. A process according to claim 14, wherein the metalis selected from the group consisting of Groups VI-B, VIII, III-A andII-B elements and their mixtures.
 17. A process according to claim 14,wherein the metal is selected from the group consisting of aluminum,indium, gallium and zinc.
 18. A process according to claim 14, whereinthe metal is in a microscopic form.
 19. A process according to claim 14,wherein the metal is in a macroscopic form.
 20. A process according toclaim 14, wherein the ionic liquid catalyst has been used to catalyze aFriedel-Craft reaction.
 21. A process according to claim 14, wherein theFriedel-Craft reaction is alkylation.
 22. A process according to claim14, wherein the ionic liquid catalyst comprises an imidazolium,pyridinium, phosphonium or tetralkylammonium derivative or theirmixtures.
 23. A process according to claim 14, wherein the ionic liquidcatalyst is a chloroaluminate ionic liquid.
 24. A process according toclaim 22, wherein the metal is aluminum.
 25. An ionic liquid catalyst,which has been regenerated in accordance with the process of claim 14.